The Sport's evolution

AUTOSPORT JULY 11, 1985 - By Martin Holmes

Hannu Mikkola made the rally debut of Audi's revolutionary second-evolution Sport Quattro within days of the design being accepted by FISA. Some 20 examples have been built and the team hope to make the World Championship debut in Finland on the 1000 Lakes, but for a trial run, Mikkola was sent to the Olympus Rally in America last weekend and duly won with ease.

During the AWA Clarion Rally of New Zealand, Audi's team manager Roland Gumpert made public for the first time many of the fundamental design objectives, aimed at regaining for Audi a competitive edge against recent four-wheel drive designs, especially from Peugeot.

"The main disadvantage with our first-evolution car was that too much weight was over the front axle. This is because the back of our production-based car has been designed to take baggage, which is not needed in rallying!

"We have therefore now put all the cooling systems in the boot, so whereas there was 58% of the weight on the front axle in the first-evolution car, our new car has 52%. Peugeot has only 45% on the front, so we will be closer to the ideal of 50/50. From tests we have already made we know the handling of the new car is better and the times are better as well".

Already the first-evolution car—used since this time, in 1984 —— has the oil radiator in the rear, but now the new car will also have the water radiator and the alternator. It is a novelty on a rally car for the alternator not to be driven directly from tile engine. "In my department we are always looking at designs for the future, and we have been considering this idea as part of this work" continued Gumpert. "It is a development of the power steering hydraulic system which uses a pump, and we have made it so that it can work as a motor for the generator. A hydraulic pipe therefore goes from the front to a pump at the rear, which drives the generator by a belt. The advantage of this system is that the generator is always working at the same speed, rather than at revolutions which always vary with the engine speed".

"We are not concerned with improving drag co-efficient..."

The additional weight of placing the water radiators in the rear is only about 8-10kg (mostly from the weight of the extra water), a small advantage compared to the benefits of better Balance. The entry of air into the rear is coupled with the objectives of the horizontal wing. "On the old car, air came over the roof. Some passed over the top of the wing and pushed it downwards —the rest passed through the oil cooler which was on top of the boot. On the second evolution car we have a much bigger wing set above the bootlid, so the airflow not only passes both sides of the wing but also directly into the boot as well. This is where the radiators are placed so the outlet is through holes in the bodywork at the rear. Some extra air enters the boot from in front of the rear wheels, and in addition to the water and engine oil, we can also use the air to cool the gearbox as well, if necessary".

"We have made many tests with the car in the wind tunnel because we have found it impossible to finalise the areodynamics without practical testing. The main objective is downforce. The heavier the force, the better. The weight of the car is always a problem, as this is pushing the car outwards during cornering, whereas downforce pushes it into the ground. With our wings, the weight at 1000kg effectively goes up from 1000kg to 1500kg and the extra 500kg is not subject to centrifugal force."

"Ground effect... is useless."

"We are not concerned with improving drag coefficient, as our engine is powerful enough for 200-230kph, we could go up to 300kph if needed, but it is not necessary. We need all the horsepower and torque for acceleration, and if we get more weight onto the tyres, we are getting better acceleration".

What is the minimum speed at which aerodynamics give an advantage? "They are already giving benefit from 10kph but of course it is not very efficient, and at 100kph it is working quite well."

And the advantage of stability? "With our wing the car is much more stable and more safe. People who say the new rally cars are getting more unsafe are not right. When we completed our recent tests in Finland, we found over the jumps it is much more safe with the wings because it is more stable in the air, and when it lands it settles down quicker. It also stops the car flying so long, which gives the driver more control".

Has Audi done any experimental work underneath the car, to create ground effect? "Not so much. You need air to cool things under the car like the exhaust, gearbox and rear differential, and then the greater priority is to make protection pieces against stones. We have tried to make ground effect work but I think it is useless because a rally car is jumping around very much. And when you jump, you lose the downforce from ground effect, and that sudden change in downforce is dangerous".

The removal of the water radiators has created new space under the bonnet, and Audi engineers have used this to help to cool down the turbo and the exhaust system, as well as intercooler. "We have put ducts to cool these items — and also the brakes—more efficiently. Of course, the less air we need for cooling, the better we can use the air for creating downforce. We have a NACA duct on the top of the wings for cooling the front brakes. Air is drawn in and sucked past the discs and out through the wheels. Ducts are also taken from the mirrors to the interior to cool the drivers, and there are holes for cooling the turbo (on the right of the bonnet) and also to help create more downforce at the front."

"Six speed automatic PDK gearbox on the RAC Rally..."

The engine has been reworked to take advantage of the extra space we have created in the front. The inlet and exhaust manifolds have been rede- signed , so the engine is more efficient and giving more torque in consequence. Everything has been rearranged, and it is possible to fit a bigger turbo, but the rules forbid the use of a twin turbo. Electronic systems are free and they have been subject to constant development all the time.

"We have not yet made big changes in the transmission. We are using the six-speed gearbox (we cannot use the alternative five-speed unit because it is too weak), but we have homologated a six-speed automatic gearbox, and we intend to use this for the first time on the RAC Rally. We have the possibility with the six-speed gearbox to change the torque split but in our car the optimum split is 50/50. We have always used this and with 52 weight in the front we do not need to do otherwise. We are now experimenting with differentials and with an automatic torque split. I think the optimum for the future will be an electronic system which limits the torque on the spinning wheel, but it does not exist! It would be like an ABS braking system in reverse".

Why an automatic gearbox? "With a normal gearbox you always have a hole. With an automatic gearbox, even when you change gear you always have torque on the wheels. This means much better acceleration, and you gain those tenths of a second on every shift".

There has however been no development of handbrake systems with the short chassis cars. "It was useful with the old long car, but the Sport Quattro is so short that a handbrake system is not necessary". The rear of the car still holds the fuel tank, located over the rear axle, while the spare wheel is also placed in the boot, although access is now by opening the rear screen

The wing on the rear is fixed as FISA limited the design of this wing, which originally would have been wider than the body. "FISA said the maximum width they would allow was the size of the Peugeot's wing, and we finally settled that the ratio of the width of the wing to the body of the Peugeot is what we should follow"

The main suspension design for evolution versions has to remain the same, but measurement of springs, and mounting points can change. Another visible change on the new car is a lateral strip below the doors from the front to the rear wings, aimed at protecting the rear from stones thrown up by the front wheels. The normal dimensions of the new car are the same as the first-evolution Sport Quattro, even the length and width are unchanged despite the aerodynamic additions "The car only looks much bigger! We have used the permitted tolerances, which are small, but that is all. We are ready to go. FISA inspected the cars on 24th June and saw all the cars except the Olympus car which was already in America, and they are happy.

We are not going to Pikes Peak with the new car, however. It was homologated but today (1st July) we plan only to use this car after Finland.